/Engine/Source/Runtime/HeadMountedDisplay/Public/IXRInput.h
Passing key events to HMD. If returns 'false' then key will be handled by PlayerController; otherwise, key won't be handled by the PlayerController.
virtual bool HandleInputKey ( class [UPlayerInput](API\Runtime\Engine\GameFramework\UPlayerInput) *, const struct [FKey](API\Runtime\InputCore\FKey) & Key, EInputEvent EventType, float AmountDepressed, bool bGamepad )